Unmanned aerial vehicles (UAVs) are remotely piloted or self-piloted aircraft that can carry cameras, sensors, communications equipment, or other payloads. A newer class of UAVs known as Micro Air Vehicles (MAVs) are essentially flying video camera systems that send video signals from the MAV to a ground control station (GCS). The video signal is less than 2 Watts in an L-band frequency (1-2 GHz) regime and needs to meet a 10 km line of sight (LOS) range requirement. Mounting an antenna on a moving vehicle and attempting to track to a moving MAV presents unique problems.
Earlier attempts to develop a di-pole omni-directional antenna have been unsuccessful at meeting or exceeding video communication range requirements for MAV systems. In order to meet the range requirements, a high gain directional logarithmic antenna was developed that gave the GCS a greater than 7.5 dBi gain and gave a greater than 10 km LOS capability to the MAV system. However, the directionality of this antenna required the operator to continually reposition the antenna for best reception of the video. This is easily accomplished in a dismounted operation where the operator can simply turn the GCS mounted antenna in the direction of the MAV, but when the operator is mounted and moving in a vehicle, adjusting the direction of the antenna is cumbersome at best. Additionally the movement of the vehicle can quickly change the direction of a fixed directional antenna mounted to the vehicle which results in a total loss of the video signal from the MAV.
Accordingly, the use of L-band frequencies and the uniqueness of the MAV/GCS geometry has made it difficult to find a commercially viable solution for meeting MAV system communication range requirements.